The present invention relates to a pneumatic radiation detector, particularly for infrared gas analysis.
A typical detector of the kind to which the invention pertains operates with two chopped (modulated) beams of infrared radiation, whereby the chopper provides the modulation in phase opposition as to the two beams. The detector is provided with two chambers for each beam, which are traversed by the respective beam serially or sequentially. These chambers are filled with particular gas and the first one of the chambers in each path has an entrance and an exit window, the respective other chambers may have only an entrance window, but it also may have an exit window. Two of the chambers in different beam paths are, for example, gas-conductively connected to opposite subchambers of a particular chamber which is biparted by a membrane, being the displaceable electrode of a variable capacitor. Pressure differences in the two subchambers are translated into an electrical signal by this capacitor. A typical device of the type referred to above is shown, for example, in US-Letters Pat. No. 3,725,702.
It was found that mechanical vibrations, impacts or other interferences may cause the membrane to vibrate, either directly or by operation of unwanted oscillatory movements of gas. Shocks may also alter the zero or any other reference point in this detector.